And from what I’ve read, T-mobile is planning to shut down 3G in July, after having previously delayed it. I’m reasonably sure all the networks have been doing this incrementally already anyway.
T-mobile, and MVNOs on T-mobile’s network, are really the only option in the U.S., as the BM818-A1’s IMEI is rejected for activation on the other networks.
Strange that AweSIM is over AT&T’s network, but the BM818-A1 is not being rejected, according to @Kyle_Rankin. (Whether or not non-VoLTE calls can connect is another story.)